Ultrathin Hybrid SiAlCOH Dielectric Films through Ring-Opening Molecular Layer Deposition of Cyclic Tetrasiloxane
Kristina Ashurbekova, Kristina Ashurbekova, Karina Ashurbekova, Karina Ashurbekova, Iva Šarić, Marco Gobbi, Evgeny Modin, Andrey Chuvilin, M. Petravić, Ilmutdin M. Abdulagatov, Mato Knez
Abstract
Molecular layer deposition (MLD) is a powerful vapor phase approach for growing thin polymer films with molecular-level thickness control. We applied the ring-opening MLD process to deposit a siloxane-alumina hybrid organic–inorganic thin film using tetramethyl-tetravinylcyclotetrasiloxane (V4D4) and trimethylaluminum (TMA) as precursors. In situ studies of this process with a quartz crystal microbalance (QCM) showed a linear mass increase with the number of MLD cycles within a processing temperature window between 120 and 200 °C. The QCM study also revealed self-limiting surface chemistry. A growth per cycle of 1.4 and 1.6 Å and a density of 1.9 and 2.2 g cm–3 were determined by X-ray reflectivity (XRR) for the V4D4/TMA film deposited at 150 and 200 °C, respectively. X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and in situ QCM were employed to analyze the structural changes and composition of the film. High-resolution transmission electron microscopy (HRTEM) was used to confirm the conformality of the obtained coatings. The grown siloxane-alumina film, even as thin as 12 nm, showed an extremely low leakage current density (lower than 5.1 × 10–8 A cm– 2 at ± 2.5 MV cm–1), a dielectric constant (k) of 4.7, and a good thermal stability after one-hour annealing in air at 1100 °C. The obtained highly conformal and thermally stable siloxane-alumina insulating film can be used as a component of field-effect transistors, flash memories, and capacitors in modern electronic systems.